You know when you get a gadget home you really need and can't wait to install and start using?
Then you realise that the new gadget has new USB thingies that weren't even on the drawing board when your old (but fabulous) computer was made... And then to figure out if USB 2.0 is the same as USB-A, or if USB 2.0 is just 'speed' and the same as USB-A... and then off into the jungle of adapters... 
Finally gave up and emailed the store I'd bought the magic mouse from to ask what was what and if they got what I need. That was before I realise that I happily plugged in my new external hard drive without any problems and that the technical instructions says it's a USB-A. So, I'm happy that I don't need to spend half the money I spent on the mouse, on an adapter, to be able to introduce the mouse to the computer. I found one at the same store I bought my external hard drive and it's very affordable. I also found a ring lamp with holder for the phone that I'd been looking for. It can be adjusted in the way that the lamp is faced down so I can record what I'm doing on a table. Something for the future. :)